ethinyl estradiol

:  a white crystalline very potent synthetic estrogen C₂₀H₂₄O₂ prepared from estrone and used in combination (as with norgestrel or norethindrone) as a birth control pill or alone in the treatment of menopausal symptoms or female hypogonadism or in the palliative treatment of prostate or breast cancer—see loestrin, minastrin, nuvaring, ortho evra, ortho-novum, ortho tri-cyclen, seasonale, seasonique, yasmin, yaz